The Lotus 99T was a Formula One car designed by Gérard Ducarouge for Lotus for use in the 1987 season. After Renault pulled out of F1 at the end of 1986, Lotus signed a deal with Honda for use of their turbocharged1.5-Litre engine, although due to Honda's already existing deal with the Williams team allowing them exclusive use of the 1987 spec Honda RA167-E, Lotus had to make do with the Honda RA166-E spec engine from 1986. As part of the deal, Lotus agreed to sign Honda's test driver Satoru Nakajima as a replacement for 1986 driver Johnny Dumfries and as team mate to Ayrton Senna. Nakajima, who many felt was only in F1 because of his nationality and because of Honda, brought little to the team other than Honda.

Lotus had also changed long time major sponsor John Player Special, replaced by Camel as title sponsor, meaning the black cars with gold sign writing the team had used in 1972-1978 and 1981-1986 were replaced by bright yellow with blue sign writing.

The 99T was the second Lotus chassis to be fitted with electronic active suspension after the team had experimented with the system on the Lotus 92 used in the first part of the 1983 season. The system's benefits of a consistent ride height with no pitch or roll in the chassis came at a cost, as the system added significant weight to the car (approx 25kg or 55lb), and also robbed the Honda turbo of approximately 5% of its power (the RA166-E was rated at approximately 900 bhp (671 kW; 912 PS) with 1987s 4.0 Bar turbo boost restriction). Ducarouge clawed as much performance back by spending many hours in the wind tunnel to compensate, although by the end of the season Senna was describing the car as nothing more than the previous year's 98T with a Honda engine instead of the Renault. The 99T was generally regarded as the more bulky of the cars that won a Grand Prix in 1987 with the Williams FW11B, McLaren MP4/3 and Ferrari F1/87 all regarded as better aerodynamically than the Lotus. Despite this, the 99T (especially in Senna's hands) was often among the fastest cars in a straight line.

After pre-season testing at the Jacarepaguá Circuit in Rio, Senna had insisted on the team using the active suspension throughout the season, feeling that due to having the previous year's engine the computer controlled system and its benefits would help keep Lotus at the front of the field (one of those benefits was that due to less tyre wear, the 99Ts were able to run less wing thus giving greater top speed). However, while the Brazilian was able to take wins on bumpy street circuits at both Monaco and Detroit, the car proved difficult to set up for other circuits.

The 99T proved to be competitive in Senna's hands; the Brazilian won twice and scored six other podium finishes during the season, helping him and the team to third in the drivers' and constructors' championships. Senna's win at the Detroit Grand Prix was the final ever Grand Prix win for the team. Senna would move to McLaren (who had secured the use of the Honda engines to replace the TAG engines used from 1983) for 1988and would win his first World Drivers' Championship. The season was also Senna's second worst in terms of pole positions, scoring only one in Round 2 at San Marino, his worst season being his rookie year in 1984 with Toleman.

Nakajima, who for his part very much overshadowed by his team mate, proved to be a steady, if unspectacular driver. He openly admitted that he favored the faster circuits such as Silverstone, Hockenheim, Österreichringand Monza as well as his home track of Suzuka, but was ill at ease on the tighter circuits. He qualified 17th in Monaco and finished 10th, 24th in Detroit before crashing out on lap 1, and 17th in Hungary before suffering a broken drive shaft on the first lap. Nakajima's best finish in his first season was a 4th at Silverstone for the British Grand Prix. He finished the season in 12th place with 7 points scored. Nakajima's best qualifying performance came in Round 15 in Japan for what was the first Japanese Grand Prix since 1977. At the Honda owned Suzuka circuit, Nakajima qualified in 11th place, only four places and 0.962 seconds behind Senna. It was the closest he would qualify to his team mate all season (as it was his home track, Nakajima had actually completed more laps at Suzuka than the entire F1 grid combined). During the season, television viewers were able to get an up close view of the Japanese rookie's driving as his car usually carried an onboard camera.

The 99T was updated for 1988 to 100T specification; the car technically was virtually unchanged, except for a redesigned nose section, longer wheelbase and tighter rear bodywork (helped by the reduction of fuel tank capacity from 1987s 195 litres to 150 litres), and the dumping of the active suspension for a more conventional setup. New team leader, 1987 World Champion Nelson Piquet (switching from Williams) used the car to score consistently but was unable to add any further wins to Lotus' score sheet however, with three 3rd placings his best finishes.

Senna's 99T was included in the Japanese and American versions of the 2001 video game Gran Turismo 3 under the alias "F687/S". The F687/S was the second most powerful Formula One car in the game (next to the F686/M) producing 900 PS (888 hp). The 99T also makes appearances in Rad Racer from Square and Continental Circus from Taito, both released in 1987.